In general, a punch unit includes a punch driver connected with a punch. The punch driver has a punch head at its back end and means for preventing relative rotation of the punch and the punch driver during a stroke of the punch. The back end of the punch is usually screw threaded into a bore at the front end of the punch driver. A pre-loaded compression means such a compression spring is provided between the punch head and a guide bushing which receives the punch to return the punch and punch driver to their rearward position. Typically, the guide bushing is connected to the remainder of the punch unit in such a manner that disassembly for removal or exchange of the punch is cumbersome. Procedures for punch length adjustment are also generally cumbersome.
Accordingly, the need exists to provide an improved punch unit having a simplified means for removing the guide bushing. A need also exists for a simplified means for effecting punch length adjustment.